Surface emission laser and manufacturing method for surface emission laser, light reception element and manufacturing method for light reception element, and optical transceiver module

ABSTRACT

The object is to provide a surface emission laser, in which low-current drive is made possible, and a manufacturing method therefor, to provide a light reception element, in which high-speed modulation is made possible, and a manufacturing method therefor, and to provide an optical transceiver module in which optical connection efficiency is improved. An opening portion  5  from the other surface  1   b  side of the semiconductor substrate  1  to the end portion on the semiconductor substrate  1  side of the light emission portion  2 A is formed on the semiconductor substrate  1  of the surface emission laser  100 , and a lens  6  made of a transparent resin is formed through the use of the side surface of the opening portion  5 . An opening portion  5  from the other surface  10   b  side of the semiconductor substrate  10  to the end portion on the semiconductor substrate  10  side of the light reception portion  20 A is formed on the semiconductor substrate  10  of the photodiode  200 , and a lens  6  made of a transparent resin is formed through the use of the side surface of the opening portion  5 . The lens  6  formed on the light emission portion  2 A of the aforementioned surface emission laser  100  and the lens  6  formed on the light reception portion  20 A of the photodiode  200  are placed facing each other without an optical waveguide therebetween.

BACKGROUND OF THE INVENTION

[0001] 1. Field of Invention

[0002] The present invention relates to a light emission element and a light reception element for the optical data communication, and to an optical transceivertransceiver module using these.

[0003] 2. Description of Related Art

[0004] Regarding a surface emission laser used for the optical communication, in order to make high-speed modulation possible, sometimes, a means of mounting by flip chip bonding without through a wire is adopted. According to this means, since the upper surface side of a semiconductor laminate of a surface emission laser is mounted by a solder bump, etc., laser light is emitted from the lower surface side of the semiconductor substrate.

[0005] However, since the wavelength emitted from a common surface emission laser is 850 nm, there has been a disadvantage in that when a gallium arsenide substrate has been used, it has been impossible to transmit the laser light.

[0006] Herein, in order to overcome the aforementioned problem, a means of making the wavelength of a surface emission laser 970 nm has been suggested in “IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 11, NO. 1, JANUARY 1999, p128-130”. According to this suggestion, it has become possible to transmit the laser light even when the gallium arsenide substrate has been used.

[0007] However, when the wavelength has been 970 nm in accordance with the aforementioned suggestion, since the sensitivity of a PIN photodiode of silicon which is used for the light reception side has been reduced, it has been necessary to use a PIN photodiode of expensive InGaAs.

[0008] Regarding the surface emission laser which is a light emission element, it is necessary to make the light emission region, to which a current is applied, narrow in order to resolve a problem of heat generation especially in the case where arraying is performed. Accompanying this, there has been a disadvantage in that the radiation angle has been increased and, therefore, the connection efficiency has been reduced. Herein, although it has been attempted to form a lens at an upper surface of the light emission portion in order to reduce the radiation angle, it has been difficult to precisely form a lens having a small curvature radius at a short distance from the light emission portion.

[0009] Furthermore, regarding the photodiode which is a light reception element, it is necessary to reduce the element capacity in order to realize the high-speed operation thereof. Accompanying this, there has been a disadvantage in that the connection efficiency with a fiber or a laser has been reduced.

[0010] Regarding the optical transceivertransceiver module for optically connecting the light emission element including the surface emission laser and the light reception element including the photodiode, it has been necessary to reduce the radiation angle of the laser light emitted from the surface emission laser and to increase the light reception area of the photodiode as large as possible.

[0011] The present invention has been made in consideration of the aforementioned circumstances. Accordingly, the object of the present invention is to provide a surface emission laser, in which the laser light of 850 nm is made possible to transmit and low-current drive is made possible, and a manufacturing method therefor, to provide a light reception element, in which high-speed modulation is made possible, and a manufacturing method therefor, and to provide an optical transceivertransceiver module, in which the optical connection efficiency is made excellent.

SUMMARY OF THE INVENTION

[0012] In order to dissolve the aforementioned problems, the invention related to claim 1 is a surface emission laser provided with a substrate, a semiconductor laminate which is formed on one surface of the substrate and which includes an light emission portion for emitting laser light, and a pair of electrodes for applying a voltage in order to pass a current in the direction of lamination of the light emission portion, wherein the aforementioned substrate includes an opening portion from the other surface of the substrate to the end portion on the aforementioned substrate side of the aforementioned light emission portion, and the opening portion is provided with a lens formed through the use of the side surface thereof.

[0013] Regarding the surface emission laser according to claim 1, since the substrate is made to include the opening portion from the other surface (that is, on the side where the semiconductor laminate has not been formed) of the substrate to the end portion on the substrate side of the light emission portion, even the laser light of 850 nm, which was hitherto impossible to pass through the gallium arsenide substrate, becomes possible to pass through. Consequently, it becomes possible to use the PIN photodiode of inexpensive silicon as an element on the light reception side.

[0014] Since the opening portion formed on the substrate is provided with the lens, the radiation angle of the laser light emitted from the light emission portion can be reduced and, therefore, it becomes possible to improve optical connection efficiency.

[0015] Since the light emission portion can be made narrow and small by being provided with a lens, low-current drive is made possible, and the problem of heat generation, which occurs in the case where arraying is performed, can be resolved.

[0016] Since it becomes possible to form the lens at the position apart from the light emission portion through the use of the side surface of the opening portion, a lens having a large curvature radius can be formed with ease. Consequently, since parallel light can be achieved even when precision of the curvature radius is not fine, it becomes possible to improve optical connection efficiency.

[0017] The invention related to claim 2 is the surface emission laser according to claim 1, wherein the opening portion is a space which becomes narrow from the other surface of the substrate toward the end portion on the substrate side of the light emission portion.

[0018] Regarding the surface emission laser according to claim 2, since the opening portion is made to be the space which becomes narrow from the other surface (that is, on the side where the semiconductor laminate has not been formed) of the substrate toward the end portion on the substrate side of the light emission portion, an inclined surface is formed on the side surface thereof. The lens having a large curvature radius can be formed with ease through the use of this inclined surface.

[0019] The invention related to claim 3 is the surface emission laser according to claim 1 or 2, wherein the lens is made of the transparent resin.

[0020] Regarding the surface emission laser according to claim 3, since the lens formed in the surface emission laser is formed by curing the transparent resin, it becomes possible to form the lens even on a small opening with ease and reliability. By adjusting the wettability between the surface of the substrate and the side surface of the opening portion, the curvature radius of the lens can be set and either of a concave lens or a convex lens can be formed. Consequently, a lens matching the predetermined conditions can be formed with ease and reliability.

[0021] The invention related to claim 4 is the surface emission laser according to any one of claims 1 to 3, wherein an emission opening for emitting the laser light is opened in the electrode formed on the surface on the side opposite to the substrate side of the light emission portion, and the laser light emitted from the emission opening is made to enter a photodiode for monitoring.

[0022] Regarding the surface emission laser according to claim 4, since the emission opening for emitting the laser light is opened in the electrode formed on the surface on the side opposite to the substrate side of the light emission portion, and the laser light emitted from the emission opening is made to enter the photodiode for monitoring, the output optical power, which varies depending on ambient temperature, etc., can be monitored, and the driving current can be controlled. Since the laser light for optical communication is emitted from the opening portion provided on the substrate side of the light emission portion, and the laser light for monitoring is emitted from the emission opening provided on the side opposite to the substrate side of the light emission portion, the surface emission laser can be arrayed at a high density, and miniaturization of the surface emission laser array becomes possible.

[0023] The invention related to claim 5 is the surface emission laser provided with a substrate, a semiconductor laminate which is formed on one surface of the substrate and which includes an light emission portion for emitting laser light, and a pair of electrodes for applying a voltage in order to pass a current in the direction of lamination of the light emission portion, wherein an emission opening for emitting the laser light is opened in the electrode formed on the surface on the side opposite to laser light emission side of the aforementioned light emission portion, and the laser light emitted from the emission opening is made to enter a photodiode for monitoring.

[0024] Regarding the surface emission laser according to claim 5, since the emission opening for emitting the laser light is opened in the electrode formed on the surface on the side opposite to laser light emission side of the light emission portion, and the laser light emitted from the emission opening is made to enter the photodiode for monitoring, in a manner similar to that in claim 4, the output optical power, which varies depending on ambient temperature, etc., can be monitored, and the driving current can be controlled. Since the laser light for optical communication is emitted from the opening portion provided on the substrate side of the light emission portion, and the laser light for monitoring is emitted from the emission opening provided on the side opposite to the substrate side of the light emission portion, the surface emission laser can be arrayed at a high density, and miniaturization of the surface emission laser array becomes possible.

[0025] The invention related to claim 6 is a manufacturing method for a surface emission laser including the step of forming a convex light emission portion for emitting laser light by etching a semiconductor laminate, which is laminated on one surface of a semiconductor substrate, in a vertical direction, the step of forming an opening portion from the other surface of the aforementioned semiconductor substrate to the end portion on the aforementioned semiconductor substrate side of the aforementioned light emission portion in order to become narrow from the other surface of the aforementioned semiconductor substrate toward the end portion on the aforementioned semiconductor substrate side of the aforementioned light emission portion, the step of injecting a transparent resin into the aforementioned opening portion, and the step of forming a lens by curing the aforementioned resin.

[0026] By the manufacturing method for the surface emission laser according to claim 6, the surface emission laser according to any one of claims 1 to 4 can be manufactured with case.

[0027] The invention according to claim 7 is the manufacturing method for the surface emission laser according to claim 6, wherein in the step of injecting the resin, the resin is injected after the wettability difference between the side surface of the opening portion and the other surface of the semiconductor substrate is adjusted.

[0028] By the manufacturing method for the surface emission laser according to claim 7, since in the step of injecting the resin, the wettability difference between the side surface of the opening portion and the other surface (that is, on the side where the semiconductor laminate has not been formed) of the semiconductor substrate is adjusted, it becomes possible to form a lens having a predetermined shape on the opening portion with ease.

[0029] The invention related to claim 8 is a light reception element provided with a substrate and a light reception portion which is formed on one surface of the substrate and into which laser light enters, wherein the aforementioned substrate includes an opening portion from the other surface of the substrate to the end portion on the aforementioned substrate side of the aforementioned light reception portion, and the opening portion is provided with a lens formed through the use of the side surface thereof.

[0030] Regarding the light reception element according to claim 8, since the opening portion from the other surface (that is, on the side where the light reception portion has not been formed) of the substrate to the end portion on the substrate side of the light reception portion is formed on the substrate, and the opening portion is provided with the lens, an equivalent light reception area of the light reception portion can be enlarged and, therefore, it becomes possible to make the light reception portion of the light reception element small. Consequently, the high-speed operation can be made possible while the optical connection efficiency of the light reception element is maintained to be excellent.

[0031] Since it becomes possible to form the lens at the position apart from the light reception portion through the use of the side surface of the opening portion, a lens having a large curvature radius can be formed with ease. Consequently, since parallel light can be achieved even when precision of the curvature radius is not fine, it becomes possible to improve optical connection efficiency.

[0032] The invention related to claim 9 is the light reception element according to claim 8, wherein the lens is made of the transparent resin.

[0033] Regarding the light reception element according to claim 9, since the lens formed in the light reception element is made of the transparent resin, effects similar to those of claim 3 can be achieved.

[0034] The invention related to claim 10 is a manufacturing method for a light reception element including the step of forming a convex light reception portion, into which laser light enters, by etching a semiconductor layer, which is formed on one surface of a semiconductor substrate, in a vertical direction, the step of forming an opening portion from the other surface of the aforementioned semiconductor substrate to the end portion on the aforementioned semiconductor substrate side of the aforementioned light reception portion in order to become narrow from the other surface of the aforementioned semiconductor substrate toward the end portion on the aforementioned semiconductor substrate side of the aforementioned light reception portion, the step of injecting a transparent resin into the aforementioned opening portion, and the step of forming a lens by curing the aforementioned resin.

[0035] By the manufacturing method for the light reception element according to claim 10, the light reception element according to claims 8 or 9 can be manufactured with ease.

[0036] The invention related to claim 11 is an optical transceiver module including the surface emission laser according to any one of claims 1 to 4.

[0037] Regarding the optical transceiver module according to claim 11, by including the surface emission laser according to any one of claims 1 to 4, it is possible to provide the optical transceiver module in which low current drive is made possible and optical connection efficiency is excellent.

[0038] The invention related to claim 12 is an optical transceiver module including the light reception element according to claim 8 or 9.

[0039] Regarding the optical transceiver module according to claim 12, by including the light reception element according to claim 8 or 9, it is possible to provide the optical transceiver module in which high-speed modulation is made possible and optical connection efficiency is excellent.

[0040] The invention related to claim 13 is an optical transceivertransceiver module including the surface emission laser according to any one of claims 1 to 4 and the light reception element according to claim 8 or 9.

[0041] Regarding the optical transceivertransceiver module according to claim 13, by including the surface emission laser according to any one of claims 1 to 4 and the light reception element according to claim 8 or 9, it is possible to provide the optical transceivertransceiver module in which low-current drive and high-speed modulation are made possible and optical connection efficiency is excellent. Furthermore, since lenses are formed in both the light emission element and the light reception element, optical data communication between IC chips, in which direct optical connection is performed without through an optical waveguide, is made possible.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042]FIG. 1 is a sectional view of a surface emission laser showing an embodiment according to the present invention;

[0043]FIG. 2 is a sectional view of a photodiode showing an embodiment according to the present invention;

[0044]FIG. 3 is a sectional view showing a manufacturing step for a surface emission laser according to the present invention;

[0045]FIG. 4 is a sectional view showing a manufacturing step for the surface emission laser according to the present invention;

[0046]FIG. 5 is a sectional view showing a manufacturing step for the surface emission laser according to the present invention;

[0047]FIG. 6 is a sectional view showing a manufacturing step for the surface emission laser according to the present invention;

[0048]FIG. 7 is a sectional view showing a manufacturing step for the surface emission laser according to the present invention;

[0049]FIG. 8 is a sectional view showing a manufacturing step for the surface emission laser according to the present invention;

[0050]FIG. 9 is a sectional view of an optical transceiver module showing an embodiment according to the present invention;

[0051]FIG. 10 is a sectional view of an optical transceiver module showing another embodiment according to the present invention; and

[0052]FIG. 11 is a sectional view of an optical transceiver module showing another embodiment according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0053] Embodiments according to the present invention will be described below with reference to drawings.

[0054]FIG. 1 is a sectional view of a surface emission laser showing an embodiment according to the present invention.

[0055] A surface emission laser 100 is a vertical resonator type surface emission laser (VCSEL), as shown in FIG. 1, and is composed of a semiconductor substrate 1 made of n-type GaAs having a thickness of 250 μm, a semiconductor laminate 2 which is formed on one surface (the lower surface in FIG. 1) 1 a side and in which a light emission portion 2A and a reinforcement portion 2B are divided with concave portion 2C therebetween, and one pair of electrodes 3 for applying a voltage in order to pass a current in the direction of lamination of the light emission portion 2A, and is mounted on a drive substrate 11 with the semiconductor laminate 2 of this surface emission laser 100 facing down.

[0056] This semiconductor laminate 2 is composed of an etching stop layer 21, an n-type DBR layer 22, an n-type spacer layer 23, an MQW active layer 24, a p-type spacer layer 25, a current constriction layer 26, a p-type DBR layer 27, and p-type contact layer 28, which are laminated in that order from one surface 1 a side of the substrate 1.

[0057] The etching stop layer 21 has a thickness of 100 nm, and is composed of an n-type Al₀ ₈Ga_(0.2)As layer. The n-type DBR layer 22 is a multi-ply layer composed of twenty-eight pairs of n-type Al₀ ₁₅Ga_(0.85)As layer and n-type Al_(0.86)Ga₀ ₁₄As layer. The n-type spacer layer 23 is composed of an n-type Al_(0.15)Ga₀ ₈₅As layer. The MQW active layer 24 is composed of three layers of quantum well layers made of GaAs. The p-type spacer layer 25 is composed of a p-type Al_(0.15)Ga₀ ₈₅As layer.

[0058] The current constriction layer 26 is made of p-type AlAs. This current constriction layer 26 is within the range of a circle having a predetermined diameter, and an insulation material layer 26 a made of aluminum oxide is formed on the periphery thereof by a few micrometers. This current constriction layer 26 is formed in order to concentrate the current from a p-type metal electrode 3A on the center portion of the light emission portion 2A.

[0059] The p-type DBR layer 27 is a multi-ply layer composed of thirty-six pairs of n-type Al_(0.15)Ga₀ ₈₅As layer and p-type Al_(0.86)Ga₀ ₁₄As layer. The p-type contact layer 28 is composed of a p-type Al₀ ₁₅Ga₀ ₈₅As layer.

[0060] Regarding this semiconductor laminate 2, these layers are sequentially laminated on one surface 1 a side of the semiconductor substrate 1 and, thereafter, a ring-shaped concave portion 2C is formed by etching in a vertical direction in order to expose the surface of the semiconductor substrate 1. Consequently, the cylindrical column-shaped light emission portion 2A and the reinforcement portion 2B on the periphery thereof are divided with the concave portion 2C therebetween. In this concave portion 2C, an insulating material 4, for example, polyimide, is embedded on the periphery of the light emission portion 2A.

[0061] The p-type metal electrode 3A is formed into the shape of a ring on the surface (the lower surface of the light emission portion 2A in FIG. 1) on the side opposite to the semiconductor substrate 1 side of the light emission portion 2A, and is contacted with the p-type contact layer 28. The ring-shaped center portion is an emission opening 7 a from which laser light for monitoring is emitted. The material for forming the p-type metal electrode 3A is composed of chromium, gold-zinc alloy, and gold.

[0062] The n-type metal electrode 3B is formed on the surface (the lower surface of the reinforcement portion 2B in FIG. 1) on the side opposite to the semiconductor substrate 1 side and the side surface of the reinforcement portion 2B in order to cover the reinforcement portion 2B and, furthermore, on a part on one surface 1 a side of the semiconductor substrate 1, and is contacted with the p-type contact layer 28. The material for forming the n-type metal electrode 3B is composed of gold-germanium alloy, nickel, and gold.

[0063] In this semiconductor substrate 1 of the surface emission laser 100, an opening portion 5 from the other surface (the upper surface in FIG. 1) 1 b side of the semiconductor substrate 1 to the end portion on the semiconductor substrate 1 side of the light emission portion 2A is formed into the shape of a quadrangular pyramid in which the base is the other surface 1 b side of the semiconductor substrate 1. On this opening portion 5, a convex lens 6, which is made of a transparent resin and which has a large curvature radius, is formed toward the other surface 1 b side of the semiconductor substrate 1. The convex shape of this lens 6 is formed by curing the part bulged due to the surface tension of the resin during injection of the transparent resin into the opening portion 5 without further treatment. Herein, as the material for forming the resin, any resin, for example, thermosetting resins, e.g., fluorinated polyimide and PMMA, and visible light or ultraviolet cure type epoxy resins, may be used as long as it is a transparent material having a wavelength of 850 nm.

[0064] Solder bumps 8 are formed on the n-type metal electrode 3B of the surface emission laser 100 having the aforementioned configuration, and mounting is performed on the drive substrate 11 including a plurality of transmitting circuits for VCSEL by flip chip bonding. On this drive substrate 11, a photodiode 7 for monitoring is formed at the position facing an emission opening 7 a of the laser light for monitoring opened in the p-type metal electrode 3A of the surface emission laser 100.

[0065] In the surface emission laser 100 having the aforementioned configuration, by applying a voltage between the p-type metal electrode 3A and the n-type metal electrode 3B, a current passes in the direction of lamination of the light emission portion 2A, and the laser light is emitted from the lens 6 provided on the opening portion 5 placed on the other surface (the upper surface in FIG. 1) 1 b side of the semiconductor substrate 1. At this time, the laser light for monitoring emitted from the emission opening 7 a formed on the surface (the lower surface in FIG. 1) on the side opposite to the semiconductor substrate 1 side of the light emission portion 2A is absorbed by the photodiode 7 for monitoring formed on the drive substrate 11 on the side opposite to the semiconductor substrate 1 side and, therefore, the output optical power can be monitored.

[0066] Next, a manufacturing method for the surface emission laser 100 according to the embodiment of the present invention will be described with reference to FIG. 3 to FIG. 8. FIG. 3 to FIG. 8 are sectional views, each showing one manufacturing step for the surface emission laser according to the present invention.

[0067] As shown in FIG. 3, the etching stop layer 21, the n-type DBR layer 22, the n-type spacer layer 23, the MQW active layer 24, the p-type spacer layer 25, the current constriction layer 26, the p-type DBR layer 27, and the p-type contact layer 28 are laminated sequentially on one surface (the upper surface in FIG. 3) 1 a of the high-resistance semiconductor substrate 1 made of GaAs.

[0068] The aforementioned each semiconductor laminate 2 is epitaxially grown by an organic metal CVD (MOCVD/Metal Organic Chemical Vapor Deposition) method. Herein, not limited to the MOCVD method, MBE (Molecular Beam Epitaxy) method may be used.

[0069] After a coating of photoresist is applied on the p-type contact layer 28, the photoresist is patterned by photolithography and, therefore, a resist layer having a predetermined pattern is formed in order to apply etching only to the periphery of the light emission portion 2A. As shown in FIG. 4, dry etching is performed using this resist layer as a mask until the semiconductor substrate 1 is exposed and, therefore, the ring-shaped concave portion 2C is formed. Herein, the cylindrical column-shaped light emission portion 2A and the reinforcement portion 2B on the periphery thereof are formed in the semiconductor laminate 2 with the concave portion 2C therebetween.

[0070] The current constriction layer 26 made of p-type AlAs is exposed under nitrogen atmosphere containing steam at about 400° C. Consequently, the AlAs layer is oxidized from the exposed surface thereof toward the inside and, therefore, an insulation material layer 26 a made of aluminum oxide is formed around the semiconductor layer made of AlAs. Herein, the insulation material layer 26 a is formed into the shape of a ring on the outer perimeter of the current constriction layer 26 on the order of 2 μm in radius remaining at the center of the light emission portion 2A.

[0071] As shown in FIG. 5, a resist 3 a is formed on the upper surface and side surface of the semiconductor laminate 2 to become the light emission portion 2A and, thereafter, 150 nm of gold-germanium alloy, 100 nm of nickel, and 100 nm of gold are evaporated in that order. Herein, the n-type metal electrode 3B is formed on the upper surface and side surface of the semiconductor laminate 2 to become the reinforcement portion 2B, and a part of one surface (the upper surface in FIG. 5) 1 a of the semiconductor substrate 1.

[0072] The resist 3 a in the preceding step is peeled off with acetone and, thereafter, as shown in FIG. 6, a resist 3 b is formed in a manner similar to that in the n-type metal electrode 3B except the upper surface of the semiconductor laminate 2 to become the light emission portion 2A. Subsequently, 100 nm of chromium, 100 nm of gold-zinc alloy, and 10 nm of gold are evaporated in that order. The resist 3 b is peeled off in a manner similar to that in the n-type metal electrode 3B and, therefore, the p-type metal electrode 3A is formed.

[0073] As shown in FIG. 7, the surface emission laser formed through the aforementioned steps is reset in order that the semiconductor substrate 1 is positioned on the upper side and, thereafter, 150 nm of silicon oxide film 5 a is formed on the other surface (the upper surface in FIG. 7) 1 b side of the semiconductor substrate 1. A resist is formed on the silicon oxide film 5 a, and a circularly opened resist pattern is formed in accordance with the center of the light emission portion 2A with a double-sided aligner. Through the use of this resist pattern, a circular opening is formed in the silicon oxide film 5 a by reactive ion etching (RIE/Reactive Ion Etching) with carbon tetrafluoride, etc. Subsequently, wet etching is performed using the silicon oxide film 5 a as a mask in a solution at 60° C. at a velocity of about 10 μm/min. Herein, the quadrangular pyramid-shaped opening portion 5, in which the base is the other surface 1 b of the semiconductor substrate 1, is formed due to the crystal structure of the semiconductor substrate 1 made of n-type GaAs. The opening diameter of the opening portion 5 on the etching stop layer 21 is made larger than the diameter of the current constriction layer 26 by more than 2 μm, and is made smaller than the diameter of the light emission portion 2A. This is for the purpose of suppressing absorption at the semiconductor substrate 1 by spreading of the laser light in the surface emission laser 100. Herein, in the present embodiment, since the diameter of the current constriction layer 26 is 4 μm, the opening diameter of the etching stop layer 21 is desirably 6 μm. Furthermore, in this wet etching, since when an isotropic etchant, for example, 3H₂SO+H₂O₂+H₂O and 5H₂PO₄, is used, the opening is formed into the shape of a circle, it is effective to form the isotropic lens 6.

[0074] After the silicon oxide film 5 a is removed in hydrogen fluoride or by dry etching, as shown in FIG. 8, the water repellency on the other surface (the upper surface in FIG. 8) 1 b of the semiconductor substrate 1 is adjusted by a plasma treatment with a carbon tetrafluoride gas. Subsequently, a transparent resin is injected into the opening portion 5 by an ink-jet (IJ) method, etc., while the mounting substrate 11 is in the condition of being held horizontally. Consequently, the resin injected into the opening portion 5 becomes in the condition that the surface is bulged due to the surface tension. Thereafter, the resin is cured using the resin property of being cured by heat, visible light, or ultraviolet ray while the mounting substrate 11 is held horizontally, and the resin is kept in the aforementioned condition. Herein, the convex lens 6 formed due to the surface tension of the resin is completed.

[0075] When the other surface 1 b of the semiconductor substrate 1 is made to have water repellency with respect to the resin, the side surface of the opening portion 5 is adjusted to have hydrophilicity with respect to the resin and, thereafter, the transparent resin is injected into the opening portion 5 by the aforementioned IJ method, etc., it is also possible to form a concave lens 6 on the opening portion 5 due to the wettability difference (not shown in the drawing).

[0076] Herein, as the method for injecting the resin into the opening portion 5, the following method can also be considered.

[0077] On the other surface 1 b side of the semiconductor substrate 1, on which the opening portion 5 has been formed, a film, for example, resist, polyimide, or SAM (Self-Assembly) film, which is different from the semiconductor substrate 1 made of GaAs, is formed. The film is removed only from the opening portion 5 by patterning, and if necessary, the wettability difference between the side surface of the opening portion 5 and the other surface 1 b side of the semiconductor substrate 1 is adjusted by the plasma treatment, etc.

[0078] The other surface 1 b of the semiconductor substrate 1 is coated with the resin while the film remaining on the other surface 1 b side of the semiconductor substrate 1 has water repellency, and the opening portion 5 has hydrophilicity.

[0079] Consequently, the resin is left only on the hydrophilic opening portion 5 due to the wettability difference between the film on the other surface 1 b side of the semiconductor substrate 1 and the side surface of the opening portion 5 and, therefore, the concave lens 6 is formed.

[0080] On the other hand, when the aforementioned SAM film, etc., are formed on the other surface 1 b of the semiconductor substrate 1 and the opening portion 5 in order to have water repellency with respect to the resin, the convex lens 6 is formed on the opening portion 5.

[0081] As described above, since the curvature radius of the lens 6 is determined depending on the wettability difference between the other surface 1 b of the semiconductor substrate 1 and the side surface of the opening portion 5, it is possible to freely change in accordance with uses. When a resin having a large refractive index is used, it becomes possible to increase the curvature radius of the lens 6 and, therefore, it becomes possible to increase the production margin. Regarding the semiconductor substrate 1 made of GaAs having a thickness of 250 μm as in the embodiment according to the present invention, it is desirable that the resin refractive index n=1.6 and the curvature radius R=on the order of 100. The lens 6 in such a condition was formed and the measurement was performed. As a result, although the radiation angle had a full angle at half maximum of 25° and, therefore, was spread when the lens 6 was not provided, the radiation angle was 6° and, therefore, narrow beam was achieved when the lens 6 was formed.

[0082] In the surface emission laser 100 according to the present invention, since the opening portion 5 from the other surface (the surface on which semiconductor laminate is not formed) side of the semiconductor substrate 1 to the end portion on the semiconductor substrate 1 side of the light emission portion 2A is formed on the semiconductor substrate 1, the laser light can be emitted from the opening portion 5. Consequently, even when a gallium arsenide substrate is used, it becomes possible to emit laser light of 850 nm and, therefore, a PIN photodiode of inexpensive silicon can be used as a light reception element.

[0083] Since the lens 6 is formed on the opening portion 5 formed in the semiconductor substrate 1, the radiation angle of the laser light emitted from the light emission portion 2A can be reduced and, therefore, it becomes possible to improve the optical connection efficiency.

[0084] Since the lens 6 is formed, it becomes possible to make the light emission portion 2A narrow and small. Consequently, low-current drive is made possible, and the problem of heat generation, which occurs in the case where arraying is performed, can be resolved.

[0085] Since the lens 6 is formed through the use of the side surface of the opening portion 5, the lens 6 can be formed at the position apart from the light emission portion 2A and, therefore, the lens 6 having a large curvature radius can be formed with ease. Consequently, parallel light can be achieved even when precision of the curvature radius is not fine and, therefore, it becomes possible to improve optical connection efficiency.

[0086] Since the lens 6 is formed by curing the transparent resin, it becomes possible to form the lens 6 even on a small opening portion 5 with ease and reliability. By adjusting the wettability between the other surface 1 b of the semiconductor substrate 1 and the side surface of the opening portion 5, the curvature radius can be set freely, and either a concave lens or a convex lens can be formed. Consequently, a lens 6 best-suited to the predetermined conditions can be formed with ease and reliability.

[0087] Since the substrate is specified to be the semiconductor substrate 1, the opening portion 5 is formed due to the crystallinity of the semiconductor substrate 1 and, therefore, the opening portion 5 having a inclined surface can be formed with ease and reliability.

[0088] Since the emission opening 7 a is formed in the electrode 3 formed on the side opposite to the semiconductor substrate 1 side of the light emission portion 2A of the surface emission laser 100, and the laser light for monitoring emitted from this emission opening 7 a is made to enter the photodiode 7 for monitoring, it becomes possible to array the surface emission laser at a high density, and it is effective for miniaturizing the surface emission laser array.

[0089] Next, a photodiode 200, which is the light reception element according to the present invention, will be described with reference to the drawings. FIG. 2 is a sectional view of a photodiode showing an embodiment according to the present invention.

[0090] The photodiode 200 is a PIN photodiode of silicon, and as shown in FIG. 2, is composed of a semiconductor substrate 10 made of p⁺-diffusion layer silicon, a semiconductor layer 20 formed on one surface (the lower surface in FIG. 2) 10 a side thereof, an insulation layer 24 a which is made of a silicon oxide film and which is formed on the surface (the lower surface in FIG. 2) on the side opposite to the semiconductor substrate 10 side of the semiconductor layer 20, and a pair of electrodes 30. This photodiode 200 is mounted on a drive substrate 110 with the semiconductor layer 20 facing down.

[0091] Regarding the semiconductor layer 20, a light absorption layer (i layer) 21 a made of a p⁻-diffusion layer is formed on one surface (the lower surface in FIG. 2) 10 a of the semiconductor substrate (p layer) 10, and an n⁺-region (n layer) 22 a surrounded by a p⁺-region 23 a is formed on the surface (the lower surface in FIG. 2) on the side opposite to the semiconductor substrate 10 side of this i layer 21 a and, therefore, a PIN photodiode is formed.

[0092] Regarding the semiconductor substrate 10 on which this semiconductor layer 20 is formed, a ring-shaped concave portion 20C is formed by etching in a vertical direction in order to expose the i layer 21 a. Consequently, the cylindrical column-shaped light reception portion 20A and the reinforcement portion 20B on the periphery thereof are divided with the concave portion 20C therebetween. In this concave portion 20C, an insulating material 40, for example, polyimide, is embedded on the periphery of the light reception portion 20A.

[0093] A p-type metal electrode 30A is formed on the surface on the side opposite to the semiconductor substrate 10 side of at least the light reception portion 20A, and an n-type metal electrode 30B is formed on the surface on the side opposite to the semiconductor substrate 10 side of the reinforcement portion 20B on which the p-type metal electrode 30A is not formed.

[0094] In the semiconductor substrate 10 of the photodiode 200, in a manner similar to that in the aforementioned surface emission laser 100, an opening portion 5 from the other surface 10 b side of the semiconductor substrate 10 to the end portion on the semiconductor substrate 10 side of the light reception portion 20A is formed into the shape of a quadrangular pyramid in which the base is the other surface 10 b side of the semiconductor substrate 10. On this opening portion 5, a convex lens 6, which is made of a transparent resin and which has a large curvature radius, is formed toward the other surface 10 b side of the semiconductor substrate 10.

[0095] Solder bumps 80 are formed on the upper surface of the p-type metal electrode 30A and the n-type metal electrode 30B of the photodiode 200 having the aforementioned configuration, and mounting is performed on the drive substrate 110 including a plurality of receiving circuits for photodiode by flip chip bonding.

[0096] Regarding the photodiode 200 having the aforementioned configuration, by applying a reverse bias voltage between the p-type metal electrode 30A and the n-type metal electrode 30B in order to make the i layer 21 a a depletion layer, the laser light made to enter from the light reception portion 20A is absorbed and is converted to a photocurrent.

[0097] Herein, regarding the photodiode 200 according to the present invention, since the opening portion 5 from the other surface 10 b side of the semiconductor substrate 10 to the end portion on the semiconductor substrate 10 side of the light reception portion 20A is formed, and the opening portion 5 is provided with the lens 6, an equivalent light reception area of the light reception portion 20A can be increased. Consequently, since the element capacity of the photodiode 200 can be reduced, it becomes possible to realize the high-speed operation of the photodiode 200 while the optical connection efficiency is maintained.

[0098] In a manner similar to that in the surface emission laser 100, since the lens 6 is formed through the use of the side surface of the opening portion 5 formed in the semiconductor substrate 10, the lens 6 can be formed at the position apart from the light reception portion 20A and, therefore, it becomes possible to form the lens 6 having a large curvature radius with ease.

[0099] Next, an optical transceivertransceiver module 300 a showing an embodiment according to the present invention will be described with reference to FIG. 9. FIG. 9 is a sectional view of an optical transceivertransceiver module showing an embodiment according to the present invention.

[0100] This optical transceivertransceiver module 300 a is composed of a surface emission laser array 101 in which the aforementioned surface emission lasers 100 are arrayed, and a photodiode array 201 in which the aforementioned photodiodes 200 are arrayed. Herein, the lens 6 formed in the light emission portion 2A of the surface emission laser 100 and the lens 6 formed in the light reception portion 20A of the photodiode 200 are laminated and placed in order to optically face each other.

[0101] In the aforementioned optical transceivertransceiver module 300 a, the laser light generated at the light emission portion 2A by the voltage applied from the drive substrate 11 including a transmitting circuit for VCSEL is emitted from the lens 6 formed on the other surface (the upper surface in FIG. 9) of the semiconductor substrate 1. This laser light enters into the light reception portion 20A from the lens 6 of the photodiode 200 placed at the facing position, and the laser light is converted to a photocurrent by being applied with a voltage from the drive substrate 110 including a receiving circuit for photodiode.

[0102] Herein, in the optical transceivertransceiver module 300 a according to the present invention, since lenses 6 are formed in both the light emission portion 2A of the surface emission laser 100 and the light reception portion 20A of the photodiode 200, it becomes possible to make the optical connection efficiency excellent without the use of an optical waveguide, for example, optical fiber. Consequently, the optical transceivertransceiver module 300 a can be provided, in which labor hours for optical axis adjustment, etc., are reduced.

[0103] Since the surface emission laser 100, in which the light emission portion 2A is made narrow and small, is used as the light emission element, low-current drive is made possible, and heat generation during arraying can be suppressed.

[0104] Since the photodiode 200 having reduced element capacity is used as the light reception element, it becomes possible to realize the high-speed operation.

[0105] Since the surface emission laser 100 and the photodiode 200 are arrayed while clearance is created therebetween, mutual interference between elements adjacent to each other can be suppressed.

[0106] An optical transceivertransceiver module 300 b showing another embodiment according to the present invention will be described with reference to FIG. 10. FIG. 10 is a sectional view of an optical transceivertransceiver module showing another embodiment according to the present invention.

[0107] This optical transceivertransceiver module 300 b is composed of a surface emission laser array 101 in which the aforementioned surface emission lasers 100 are arrayed, a photodiode array 201 in which the aforementioned photodiodes 200 are arrayed, and a pair of mirror devices 400. Herein, the surface emission laser array 101 and the photodiode array 201 are placed side by side on the same surface. Both the lens 6 formed in the surface emission laser 100 and the lens 6 formed in the photodiode 200 face up. A first mirror device 400 a of the pair of mirror devices 400 is formed above the light emission portion 2A of the surface emission laser 100, and a second mirror device 400 b is formed above the light reception portion 20A of the photodiode 200.

[0108] Herein, the laser light emitted from the light emission portion 2A of the surface emission laser 100 impinges on the mirror device 400 a and is reflected so as to impinge on the second mirror device 400 b. The laser light impinged on the second mirror device 400 b is reflected so as to enter the light reception portion 20A of the photodiode 200.

[0109] In this optical transceivertransceiver module 300 b, since lenses 6 are formed on both the light emission portion 2A of the surface emission laser 100 and the light reception portion 20A of the photodiode 200, the radiation angle of the laser light is reduced and, therefore, it becomes possible to perform optical connection through the use of reflection of the mirror device 400. At this time, when this mirror device 400 is made movable, and the case where the laser light impinges and the case where the laser light does not impinge are adjusted, it is expected to use the mirror device 400 as switching of the optical transceivertransceiver module 300 b.

[0110] An optical transceivertransceiver module 300 c showing another embodiment according to the present invention will be described with reference to FIG. 11.

[0111] This optical transceivertransceiver module 300 c is composed of a surface emission laser array 101 in which the aforementioned surface emission lasers 100 are arrayed, a photodiode array 201 in which the aforementioned photodiodes 200 are arrayed, and optical fibers 500. Herein, the optical fiber 500 is connected between the light emission portion 2A of the surface emission laser 100 and the light reception portion 20A of the photodiode 200.

[0112] Herein, since the light emission portion 2A and the light reception portion 20A are connected with the optical fiber 500, it is possible to stabilize the optical connection efficiency of the laser light. However, in order to use the optical waveguide, for example, the optical fiber 500, each of the optical axes of the surface emission laser 100, the optical fiber 500, and the photodiode 200 must be adjusted.

[0113] Herein, in the present embodiment, the PIN photodiode has been used as the light reception element. However, not limited to this, any light reception element, for example, a phototransistor, may be used. Regarding the optical transceivertransceiver module 300 according to the present invention, it is not limited to the present embodiment as long as the lens 6 is formed in at least one of the light emission element and the light reception element.

[0114] In the present embodiment, respective semiconductor substrates 1 and 10 of the surface emission laser 100 and the photodiode 200 are not limited to this, and it is possible to use other substrates.

[0115] As described above, according to the surface emission laser of the present invention, since the opening portion from the other surface (that is, on the side where the semiconductor laminate has not been formed) of the substrate to the end portion on the substrate side of the light emission portion has been formed, it has become possible to pass through the laser light of 850 nm even when the gallium arsenide substrate has been used.

[0116] Since the lens is provided on the opening portion, it becomes possible to provide the surface emission laser in which the optical connection efficiency is improved and low-current drive is made possible.

[0117] Since the lens can be formed at the position apart from the light emission portion through the use of the side surface of the opening portion, it becomes possible to form the lens having a large curvature radius with ease.

[0118] Since the lens is made of a transparent resin, it becomes possible to form the lens best-suited to the predetermined conditions even on a small opening portion with ease and reliability.

[0119] In particular, by the surface emission laser according to claims 4 and 5, it becomes possible to array the surface emission laser at a high density, and miniaturization of the surface emission laser array becomes possible.

[0120] According to the light reception element of the present invention, since the opening portion from the other surface (that is, on the side where the light reception portion has not been formed) of the substrate to the end portion on the substrate side of the light reception portion is formed, and the opening portion is provided with the lens formed through the use of the inclined surface thereof, it becomes possible to provide the light reception element in which the optical connection efficiency is improved and high-speed modulation is made possible.

[0121] By the optical transceivertransceiver module according to the present invention, it becomes possible to provide the optical transceiver module in which optical connection efficiency is made excellent and low-current drive and high-speed modulation are made possible. 

What is claimed is:
 1. A surface emission laser comprising a substrate, a semiconductor laminate which is formed on one surface of the substrate and which includes an light emission portion for emitting laser light, and a pair of electrodes for applying a voltage in order to pass a current in the direction of lamination of the light emission portion, wherein the substrate includes an opening portion from the other surface of the substrate to the end portion on the substrate side of the light emission portion, and the opening portion comprises a lens formed through the use of the side surface thereof.
 2. The surface emission laser according to claim 1, wherein the opening portion is a space which becomes narrow from the other surface of the substrate toward the end portion on the substrate side of the light emission portion.
 3. The surface emission laser according to claim 1, wherein the lens is made of a transparent resin.
 4. The surface emission laser according to claim 1, wherein an emission opening for emitting the laser light is opened in the electrode formed on the surface on the side opposite to the substrate side of the light emission portion, and the laser light emitted from the emission opening enters a photodiode for monitoring.
 5. A surface emission laser comprising a substrate, a semiconductor laminate which is formed on one surface of the substrate and which includes an light emission portion for emitting laser light, and a pair of electrodes for applying a voltage in order to pass a current in the direction of lamination of the light emission portion, wherein an emission opening for emitting the laser light is opened in the electrode formed on the surface on the side opposite to the laser light emission side of the light emission portion, and the laser light emitted from the emission opening enters a photodiode for monitoring.
 6. A manufacturing method for a surface emission laser, comprising: the step of forming a convex light emission portion for emitting laser light by etching a semiconductor laminate, which is laminated on one surface of a semiconductor substrate, in a vertical direction; the step of forming an opening portion from the other surface of the semiconductor substrate to the end portion on the semiconductor substrate side of the light emission portion in order to become narrow from the other surface of the semiconductor substrate toward the end portion on the semiconductor substrate side of the light emission portion; the step of injecting a transparent resin into the opening portion; and the step of forming a lens by curing the resin.
 7. The manufacturing method for a surface emission laser according to claim 6, wherein in the step of injecting the resin, the resin is injected after the wettability difference between the side surface of the opening portion and the other surface of the semiconductor substrate is adjusted.
 8. A light reception element comprising a substrate and a light reception portion which is formed on one surface of the substrate and into which laser light enters, wherein the substrate includes an opening portion from the other surface of the substrate to the end portion on the substrate side of the light reception portion, and the opening portion comprises a lens formed through the use of the side surface thereof.
 9. The light reception element according to claim 8, wherein the lens is made of a transparent resin.
 10. A manufacturing method for a light reception element, comprising: the step of forming a convex light reception portion, into which laser light enters, by etching a semiconductor layer, which is formed on one surface of a semiconductor substrate, in a vertical direction; the step of forming an opening portion from the other surface of the semiconductor substrate to the end portion on the semiconductor substrate side of the light reception portion in order to become narrow from the other surface of the semiconductor substrate toward the end portion on the semiconductor substrate side of the light reception portion; the step of injecting a transparent resin into the opening portion; and the step of forming a lens by curing the resin.
 11. An optical transceiver module comprising the surface emission laser according to claim
 1. 12. An optical transceiver module comprising the light reception element according to claim
 8. 13. An optical transceiver module comprising the surface emission laser according to claim 1 and a light reception element having a substrate and a light reception portion which is formed on one surface of the substrate and into which laser light enters, wherein the substrate includes an opening portion from the other surface of the substrate to the end portion on the substrate side of the light reception portion, and the opening portion comprises a lens formed through the use of the side surface thereof. 